As known to those skilled in the art, a surface rewinder is generally used for producing smaller diameter logs, or rolls, of web material wound upon a central core from large diameter parent rolls. Typically, these machines are used in the paper converting industry to produce rolls of bath tissue, kitchen towels, all purpose wipes, and the like. It is known that formed logs of web material may be as long as 510 centimeters and have an outer diameter of about 10 to 15 centimeters. The formed logs of web material are then subsequently cut transversely to their axis to obtain small rolls of wound web material that may have a length ranging from 10 to 30 centimeters in length.
Several types of surface rewinders are commercially available. One available type of surface rewinder is embodied as a three-drum cradle. Exemplary three-drum cradle surface rewinders are described in U.S. Pat. Nos. 4,327,877; 4,487,377; 4,723,724; 4,828,195; 5,979,818; 6,648,266; U.K. Patent No. 2,105,688; and EPO Patent EP-A-0 498 039. Another exemplary surface rewinder utilizes a speed change among a plurality of rollers to move logs of partially wound web material from one side of a pair of winding rollers to the other. Such an exemplary surface rewinder is described in U.S. Pat. No. 4,327,877. Yet still another type of surface winder utilizes a moveable winding drum. Exemplary moveable winding drums are detailed in U.S. Pat. No. 4,909,452.
Even though certain of these exemplary surface rewind machines are commercially available, those of skill in the art have realized that these machines have certain drawbacks. Primary among these drawbacks is the fact that product produced from these exemplary rewind systems are known to have non-uniform wind profiles. A typical non-uniformly wound product generally exhibits a non-uniform wind profile by having visually observable tight and loose portions in the wound roll. Such tight and loose portions in the wound roll can be shown by the use of conventional measurement techniques known by those of skill in the art.
Additionally, certain of these exemplary surface rewind systems are known to provide wound rolls having significant compression of the wound sheets near the core of the roll. This requires a looser wind for the rest of roll to achieve the desired product diameter when winding a product of fixed wound length, resulting in the finally wound product having a higher average compressibility than a corresponding uniformly wound web material. Additionally, certain of the exemplary surface rewind systems can cause logs to become unstable during the winding of low-density wound rolls. Such log instability can limit the speed of the rewinder as well as the rewinder throughput capability.
In an attempt to deal with these winding problems, currently available surface rewinding equipment requires the operator to provide adjustment of multiple, and complex, control settings that are interdependent and not related to the theory of the winding process. This complexity adds a high degree of uncertainty in the ability to provide a process that produces a uniformly wound product.
Many of the multiple control settings generally control the lower roller speed of a surface rewinder. These multiple control settings define the amount of deceleration and the duration of deceleration of the lower roller relative to the other rollers throughout the winding cycle. As the winding progresses throughout the winding cycle, the lower roller speed typically transitions linearly between these defined control settings. Thus, it should be clear that these current surface rewinder control methods are non-theoretically based and cause non-uniformly wound rolls. This approach can be particularly problematic when winding low-density products having large diameters with little total wound paper length.
Thus, there is a need to provide a true theoretical winding control process with simplified operator controls that is capable of producing a desired winding profile. Such a preferred theoretical process should be based upon the principle of winding a web material uniformly about a core. It is believed that such a theoretical process can provide the unique capability to deliver a more consistent and uniform wind and can increase the capability, throughput, and product compatibility of a surface rewinding process.